Process and installation for the combined generation of electrical and mechanical energy

ABSTRACT

The invention relates to a process for the combined generation of electrical and mechanical energy from the oxidation of fuel. In particular a hydrogen-containing gas is generated by endothermic reaction of hydrocarbon compounds, in which a portion of the hydrogen-containing gas is burned for generating a combustion gas. An oxygen-containing gas is then compressed and introduced into the combustion stage, and the energy is generated by expanding the hot combustion gas in at least one gas turbine. Further, the expanded combustion gas is used for indirect heating of the endothermic reaction. According to the present invention, at least a part of the generated hydrogen-containing gas is to be guided as anode gas through a fuel cell system for generating electrical energy and the anode exhaust gas is used for generating the combustion gas.

FIELD OF THE INVENTION

The invention relates to a process for the combined generation ofelectrical and mechanical energy from the oxidation of fuel, as well asto an apparatus for carrying out the process.

BACKGROUND OF THE INVENTION

In most thermal power stations electrical energy is generated by firstproducing superheated steam by means of burning fossil fuels in boilerinstallations. The steam is expanded in steam turbines and, in doing so,converted into mechanical energy. The steam turbines are coupled withelectric generators so that this mechanical energy is converted intoelectrical energy. This is effected with an efficiency of well over 90%.On the other hand, the efficiency of the conversion of the energychemically bonded in the utilized fuel into mechanical energy is quitemodest, as the turbine efficiency is at most approximately 37% even inlarge turbines, and losses in the heating boiler must also be taken intoaccount.

Therefore, in many cases only roughly 35% of the heat released duringcombustion could previously be effectively used for generatingelectricity, while roughly 65% was lost as exhaust heat or could only beused purely for heating purposes.

More recently, a considerable increase in mechanical or electricalefficiency was achieved by employing a combination of gas turbines andsteam turbines for converting the thermal energy into mechanical energy.The hot combustion gases are first expanded in gas turbines and the heatof the exhaust gas of these gas turbines is used for generating thesteam for the steam turbines. Other possibilities for improvementconsist in guiding the expanded steam flowing out of a steam turbineback into the combustion chamber of the gas turbine connected upstream,thus generating a greater volume flow for driving the gas turbine. Thesesteps have made it possible to raise the efficiency of the conversion ofthermal energy into mechanical energy in larger plants (over 50 MW) inthe order of magnitude of approximately 48 to 50%.

A process and an installation for generating mechanical energy fromgaseous fuels is known from the European Patent 0 318 122 A2, in whichthe mechanical energy which can be used, for example, to generatecurrent is delivered solely by means of a gas turbine, rather thanpartially by means of a steam turbine. This gas turbine, which isprovided particularly for an output range of 50 to 3000 KW, achieves anefficiency of approximately 42% with respect to the utilized thermalenergy (net calorific value). To this end, combustion air is firstcompressed in a compressor. The compressed combustion air is then heatedin an exhaust gas heat exchanger, partially expanded via a first gasturbine which only drives the compressor, and subsequently fed to acombustion chamber in which fuel is burned with this combustion air.

The hot exhaust gas formed during combustion drives a second gas turbinewhich supplies the actual usable mechanical energy. The still hotexhaust gas flowing out of the second gas turbine is used for operatingthe exhaust gas heat exchanger for heating the compressed combustionair.

In the German Patent 40 03 210.8, which was not published beforehand,the Applicants already suggested a process for generating mechanicalenergy which can be converted into electrical energy by means of anelectric generator. This process provides that a starting fuel based onhydrocarbon compounds is first converted in a steam reformation into ahydrogen-rich gas of superior value from an energy standpoint beforethis hydrogen-rich gas is burned in one or more combustion chambers. Thecombustion is effected by means of a compressed oxygen-containing gas(e.g. compressed air). The generated hot combustion gas is expanded in agas turbine generating the externally deliverable or output mechanicalenergy, is correspondingly cooled off and then used for indirect heatingof the steam reformer. The combustion gas which is further cooled in thesteam reformer is then used for heating the compressed combustion air ina further indirect heat exchange. The compressed combustion airaccordingly obtains so much energy that it can be partially expanded ina gas turbine before being used for the combustion and thus supplies therequired drive energy for generating compressed air. In another variantof this process, the compressed combustion air which is heated by theindirect heat exchange is first guided into a combustion chamber and isthere burned with a portion of the hydrogen-rich gas so that a stillhotter gas is available for expansion in the gas turbine.

This process makes it possible to increase the efficiency of theconversion of the energy (net calorific value H_(u)) contained in aconventional fuel (e.g. natural gas or biogas) into mechanical energy ata reasonable cost in small plants (up to approximately 3 MW output) byat least 50% and in larger plants by at least 55%.

As a rule, it is provided in such processes ultimately to convert thegenerated mechanical energy into electric current. This is becauseenergy can be most easily transported to the desired location with anenergy requirement in this form and can be converted back into otherforms of energy (e.g. mechanical or thermal) with high efficiency in acomparably simple manner. On the other hand, the increasing demand forsubstantial reductions in CO₂ and other pollutants (particularly NO_(x),SO_(x)) formed in the conversion of fuels into electric current ormechanical energy must be taken into account. With respect to CO₂, thisdemand can be met without incurring the costs for separating CO₂ fromthe occurring exhaust gases only if the energy chemically bonded in theutilized fuel is converted in a considerably more efficient manner thanwas previously the case. Thus there is a need for a further increase inthe efficiency of energy conversion not only for purely economic reasonsbut also for purposes of environmental protection.

OBJECT OF THE INVENTION

The object of the invention is therefore to provide a process and aninstallation for implementing this process which allows the conversionof the energy chemically bonded in a fuel (net calorific value H_(u))into electrical and mechanical energy with an efficiency of at least60%, possibly even more than 65%.

Other objects and features of the present invention will become apparentfrom the following detailed description considered in conjunction withthe accompanying drawings. It is to be understood, however, that thedrawings are designed solely for the purposes of illustration and not asa definition of the limits of the invention, for which reference shouldbe made to the appended claims.

This object is met by a process with the features of patent claim 1.This process can be advantageously developed according to the inventionby means of the characterizing features of subclaims 2 to 21. Aninstallation for carrying out this process has the features of patentclaim 22 and can be advantageously developed by means of thecharacterizing features in subclaims 23 to 44.

SUMMARY OF THE INVENTION

The invention is based on the idea of converting a conventional fuelinto a richer hydrogen-containing fuel by an endothermic reaction (e.g.steam reformation) initially by making use of exhaust heat and thenusing at least a portion as fuel in a fuel cell for the directgeneration of electrical energy. A majority of the hydrogen content isconsumed by oxidation. The remaining residual hydrogen content and theother combustible components (CO and unconverted hydrocarbon compounds)of the original hydrogen-rich gas are then supplied for burning. The gasprovided for combustion can be a mixture of different gas flows formedin the process and can be further enriched by proportions of the primaryfuel. The hot combustion gases which are accordingly formed are expandedin a gas turbine system and used for generating mechanical or (whencoupled with an electric generator) additional electrical energy. Indoing so, it is important that the thermal energy released in theprocess be converted extensively into the energy forms ultimately aimedfor by making the best possible systematic use of the exhaust heatenergy. This is effected particularly in that the combustion gasexpanded in the gas turbine system, or a partial flow of this combustiongas, is used first to supply heat to the steam reformation process andthen additionally for heating the compressed oxygen-containing gasrequired for generating the combustion gas.

Before the extensively cooled combustion gases are released into theatmosphere, they can be also be used, beyond the generation ofelectrical and mechanical energy, for the purposes of a power/heatcoupling for express heating purposes (e.g. heating buildings,hot-houses, etc.) and accordingly make increased use of energy. Withrespect to the net calorific value of the utilized fuel, the electricalefficiency of the process according to the invention can be increased by60 to 80% (typically 65-75%) depending on the embodiment form. Theinvention can be carried out with one or more gas turbines, with one ormore steam reformation installations, with one or more fuel cells, andwith one or more combustion chambers for generating the requiredcombustion gas. In addition, one or more steam generators and one ormore steam turbines can also be provided. Also, connection techniquescan be used for serial or parallel connection of identical units. Inthis context, "fuel cell" refers to any combination of connected fuelcell elements.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings, wherein like reference characters denote similarelements throughout the several views:

FIG. 1 is a schematic drawing of the first embodiment of the presentinvention;

FIG. 2 is a schematic drawing of the second embodiment of the presentinvention;

FIG. 3 is a schematic drawing of the third embodiment of the presentinvention;

FIG. 4 is a schematic drawing of the fourth embodiment of the presentinvention; and

FIG. 5 is a schematic drawing of the fifth embodiment of the presentinvention.

The invention is explained in more particular detail with reference tothe embodiment forms shown by way of example in FIGS. 1 to 5. Thedrawings show a schematic diagram of an entire installation, or asection thereof, according to the invention.

DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENTS

In FIG. 1, the installation according to the invention has a compressorsystem K which includes two compressor stages K1 and K2 and in which anoxygen-containing gas (preferably air) is compressed to a higherpressure. This gas is sucked in through the pipeline I and reaches thesecond compressor stage K2 via the pipeline 2 of the first compressorstage K1.

A heat exchanger which effects an intermediate cooling of the partiallycompressed oxygen-containing gas and discharges the extracted heat via acooling circuit 3 is connected in the pipeline 2. The discharged heatcan be used, if desired, for heating purposes external to the process.

However, it is also possible in principle to make use of this heat e.g.to preheat water for generating process steam in the process itself. Ofcourse, the compressor system K can also be constructed in one stage orin more than two stages.

The compressed oxygen-containing gas leaves the final compressor stageK2 via pipeline 4 and arrives in an indirectly heated heat exchanger W.After the increase in temperature has been effected, theoxygen-containing compressed gas is guided through pipeline 5 into acombustion chamber B in which, accompanied by formation of a hotcompressed combustion gas, it undergoes an exothermic reaction with agas which contains hydrogen and possibly other combustible componentsand is fed via the pipeline 15. In addition to the hydrogen-containinggas, primary fuel (e.g. natural gas) can also be burned (at leastintermittently). The hot combustion gas exits the combustion chamber Bvia a pipeline 6 and is expanded in a gas turbine T until close to theoperating pressure of a fuel cell FC. The mechanical energy occurring inthe gas turbine T is used in part (e.g. via a mechanical coupling) fordriving the compressor system K and in part for generating electricalalternating current in the adjoining generator G.

The extensively expanded combustion gas, which is however still hot, isthen directed as heating medium through the pipeline 7 into anindirectly heatable steam reformer R. The steam reformer R can becharged with gaseous hydrocarbons (primary fuel) and steam via apipeline 13 so that a hydrogen-rich gas is formed therein which is drawnoff via the pipeline 14. The combustion gas which is further cooled inthe steam reformer R still contains considerable heat. Therefore, it isguided via pipeline 10 into the heat exchanger W where it causes theabove-mentioned increase in temperature in the oxygen-containing gaswhich is under increased pressure. The combustion gas can then be guidedoff.

Of course, the residual heat energy can also be exploited (e.g. forpreheating process water or heating buildings). In the present example,this heat energy is exploited in another manner prior to its finaldischarge. This requires that combustion be effected in the combustionchamber B with a surplus of oxygen. That is, the extensively cooledcombustion gas can be fed as cathode gas via pipeline 11 to the fuelcell FC and can cover its oxygen requirement. Only then is it guided offthrough the pipeline 12.

The hydrogen-rich gas required as fuel for the fuel cell FC is fedthrough the pipeline 14 to the anode space of the fuel cell FC. Anelectrical direct current is generated due to the electrochemicaloxidation process in the fuel cell FC and is discharged via the line 16and, if necessary, can be converted into alternating current by means ofan electric inverter, not shown in the drawing. The direct current canalso be fed directly to the generator G.

As it is always only a part of the hydrogen content of the hydrogen-richgas that is converted in the fuel cell FC and additional combustible gascomponents (e.g. CO and unconverted hydrocarbons) can be contained, theanode exhaust gas from the fuel cell FC is fed through pipeline 15 tothe combustion chamber B as fuel. In addition, another portion of theprimary fuel can also be fed to the combustion chamber B directly, i.e.without previous conversion by endothermic reaction, to cover the heatrequirement. This is advisable particularly for starting up the processand can also simplify regulation. A compressor, not shown in thedrawing, can be provided in the pipeline 15 to bring the anode exhaustgas to the pressure required in combustion chamber B. However, thereformer R can also be operated with a suitable overpressure in itsreaction space so that the anode gas in the pipeline 14 is alreadyavailable with sufficient pressure. However, this requires thatstructural arrangements be made at the fuel cell FC for allowing acorresponding pressure difference between the anode and cathode space.

The fuel cell FC is preferably operated in such a way that the remainingcalorific value of the anode exhaust gas is sufficient to ensure theheating of the steam reformer R and to allow mechanical energy to begenerated in the gas turbine T beyond the energy requirement for drivingthe compressor system K. The arrangement of the fuel cell system FCeffected at the end of the process on the exhaust gas side isparticularly advantageous when a type of fuel cell is employed whichworks at relatively low operating temperatures. Fuel cells withelectrolytes based on phosphoric acid (PAFC), alkali (AFC) or solidpolymers (SP(E)FC) are particularly suitable.

FIGS. 2 to 5 show additional schematic embodiment forms of the inventionwhich fundamentally conform to the construction in FIG. 1.

Parts of the installation which share the same function have thereforebeen provided with the same reference numbers. Therefore, onlymodifications need be discussed in more detail in the following.

In FIG. 2, two gas turbines are provided, the first gas turbine KT beingresponsible exclusively for driving the compressor system K, while thesecond gas turbine T generates the mechanical energy which can beoutput. With such a distribution of labor between the gas turbines KTand T it is also possible in principle, as distinct from the drawing, toarrange these gas turbines on a common shaft. A substantial differencecompared to FIG. 1 consists in that the combustion chamber B is onlyarranged after the compressor drive turbine KT. The compressor driveturbine KT is therefore driven solely by the partial expansion of theadequately heated compressed combustion air in the heat exchanger W. Afurther difference consists in that the fuel cell FC is not arranged atthe end of the process on the exhaust gas side. Rather, the combustiongas is guided, via the pipeline 10d, into the cathode space of the fuelcell system FC immediately after leaving the heating space of the steamreformer R. Only then does it arrive in the heat exchanger W through apipeline 12a for indirect heating of the compressed combustion air. Thisarrangement is preferred for fuel cell types with a higher operatingtemperature (e.g. in melt-carbonate (MCFC) or solid-oxide fuel cells(SOFC)).

The variant of the process shown in FIG. 3 has two separate gas turbinesKT and T, as is the case in FIG. 2. However, the combustion of thecombustible components of the anode exhaust gas of the fuel cell systemFC takes place in two combustion chambers B1 and B2 which are arrangedrespectively immediately prior to one of the two gas turbines KT and T.

This gas turbine KT can also be used for generating mechanical orelectrical energy, since the compressed gas which can be expanded in thecompressor drive turbine KT and which covers the total requirement ofoxygen for the process can be raised by means of the combustion chamberB1 to a substantially higher energy level than would be practicable ifthe temperature increase were effected solely by means of the indirectheat exchange in the heat exchanger W. Therefore, an additional electricgenerator GK (shown in dashed lines) is coupled to the compressor driveturbine KT in the drawing.

Another possible modification of the process according to the inventionconsists in the use not only of a plurality of gas turbines andcombustion chambers, but also a plurality of steam reformers. The lattercan be connected in parallel, for example. But it is particularlyadvantageous to connect them in series, as is shown in dashed lines inFIG. 3. The first steam reformer R1 is connected immediately subsequentto the compressor drive turbine KT. The cooled combustion gas whichflows out of the heating space of the steam reformer R1 and still has aconsiderable oxygen content is directed into the second combustionchamber B2 via the pipeline 8. A partial flow 15b of the anode exhaustgas drawn off through pipeline 15 is burned in this combustion chamberB2, while the other partial flow 15a is burned in the first combustionchamber B1. The combustion process in the second combustion chamber B1creates a hot flow of combustion gas constituting a correspondinglygreater quantitative flow compared with the combustion gas flowing outof the first combustion chamber B1. It is guided through the pipeline 9to the gas turbine T, expanded above the given operating pressure of thefuel cell FC, and guided further through the pipeline 10. But thecombustion gas is not then guided through the pipeline segment 10a ofthe line 10, but rather arrives in the heating space of the second steamreformer R2 via the pipeline 10c, shown in dashed lines, and is guidedback into the pipeline segment 10b of line 10 via the pipeline 10d afteryielding heat. This line 10 leads directly to the heat exchanger W asshown in FIG. 1. The steam reformer R2 is supplied with gaseoushydrocarbons and steam via the. pipeline 13a, shown in dashed lines. Thehydrogen-rich gas formed in the steam reformer R2 is guided to line 14through pipeline 14a and reaches the anode space of the fuel cell systemFC together with the hydrogen-rich gas formed in the steam reformer R1by way of pipeline segment 14b. Of course, the fuel cell system FC canbe made up of a plurality of individual fuel cells.

FIG. 3 shows two further developments of the process which can beadvantageous in many cases. For example, the hydrogen-rich gas can besubjected to a CO/H₂ shift reaction in one or more reactors S beforebeing supplied to the fuel cell FC to increase the hydrogen content.This is an exothermic reduction, wherein the conversion of CO with watervapor to form CO₂ and H₂ causes an increase in the hydrogen component.Moreover, it is advisable in fuel cells which are sensitive to certaingas components (e.g. CO) to provide a corresponding gas purification P(e.g. by means of diaphragms or pressure shift adsorption PSA). Such agas purification is also advantageous for increasing the fuel cellefficiency. As shown in FIG. 3, the separated gas, insofar as itcontains combustible components, is preferably supplied directly to thecombustion chambers B1 and B2.

The invention is shown schematically in FIG. 4 in an embodiment formwhich includes an additional steam turbine process for generating energyand accordingly enables a substantial increase in overall efficiency inthe conversion of the energy bonded in the utilized primary fuel (netcalorific value) into mechanical and electrical energy up to an order ofmagnitude of 70-80%. In contrast to FIG. 3, the compression of thecombustion air is effected in the compressor system K withoutintermediate cooling, that is, in only one stage. However, in order toachieve the highest possible compression it is advantageous to take inair which is already cooled beforehand through the pipeline 1. Further,a heat exchanger W1 is inserted into the pipeline 14b in which thehydrogen-rich gas flows (lines 14 and 14a) generated in the steamreformers R1 and R2 are combined. The heat exchanger W1 causes anindirect exchange of the heat of the hydrogen-rich gas for preheatingthe combustible, hydrogen-containing gas which is guided throughpipelines 15 (of the fuel cell FC) and 17 (of the gas purification P)and directed to the heating spaces of the steam reformers R1 and R2through pipeline 15a and 15b.

A further difference with respect to FIG. 3 consists in that FIG. 4shows two steam generators D₁ and D₂ in which live steam is produced byindirect heat exchange with the hot combustion gas and can be used toadvantage for generating the hydrocarbon/steam mixture (reformercharging material), although this is not shown in the drawing. Otheradvantageous possible uses for the generated steam are for cooling theturbine blades and introducing steam into the combustion chambers B1 andB2 to increase the mass flow.

Whereas the steam generator D₁ is connected into the pipelines 11 and11a and the combustion gas is cooled approximately to the operatingtemperature of the fuel cell FC, the steam generator D₂ is installed inpipeline 12c, through which only a portion of the cathode exhaust gas(line 12a) is guided. The other part of the cathode exhaust gas arrivesin an indirectly heated air preheater LW₂ in a secondary flow throughpipeline 12b as heating medium and is then guided into the pipeline 12cagain. In this embodiment form of the invention, the oxygen content inthe combustion gas is, by itself, generally no longer sufficient toensure the supply of cathode gas to the fuel cell system FC. Therefore,an additional flow of fresh air is guided through the pipeline 18 intothe cathode space of the fuel cell system FC. In addition to the airpreheater LW₂, an air preheater LW₁ is provided for heating this extraair flow roughly to the operating temperature of the fuel cell systemFC, the extra air flow being brought to operating pressure by means of acompressor V. The air preheater LW₁ is inserted into line 12 on theheating side, the extensively cooled combustion gas being guided offthrough this line 12.

These modifications of the invention could also be applied within theframework of the embodiment forms according to FIGS. 1-3. However, asubstantial advance with respect to the highest possible efficiency ofenergy conversion is achieved particularly by the additionalincorporation of a steam turbine process into the process according tothe invention. The additional plant technology essential for thispurpose is enclosed by dash-dot lines and displayed in FIG. 4.

Before entering the air preheater LW₁ after passing through the steamgenerator D₂ or air preheater LW₂, the combustion gas, which isgenerally expanded virtually to atmospheric pressure, is split into twodifferent partial flows in a separating installation MD (e.g. diaphragmfilter), namely into a genuine exhaust gas flow directed out through theline 12 and a steam flow directed out from the separating installationMD through the separate line 23. It is essential that the waterproportion contained in the combustion gas be separated out in thisseparating unit MD in the form of steam, rather than in liquid form(e.g. by means of condensers). Because of its low pressure, this steamis fed via a corresponding low-pressure steam inlet to a steam turbineTD and is expanded therein. This is made possible in that the condenserC connected to the steam turbine TD via the line 19 is operated undervacuum. If the gaseous components of the combustion gas flow were notseparated out in the separating unit MD, the required vacuum in thecondenser could not be maintained in a technically and economicallyfeasible manner.

In addition, the steam turbine TD is acted upon by steam at a higherpressure via the line 22b. This steam is generated in connection withthe cooling of the fuel cell system FC which is explained, though notshown separately, in the other drawings. For this purpose, a portion ofthe condensate produced in the condenser C is used as cooling fluid andis fed via line 20 and line 22a to the cooling system of the fuel cellsystem FC. Surplus condensate can be drawn off through line 21 and used,for example, to generate steam in the steam generators D₁ and D₂ or asvaluable demineralized water in other processes. Since the processaccording to the invention is based on a progressive oxidation of H₂ toform H₂ O, a surplus of water and accordingly a valuable by-product iscompulsorily produced.

The mechanical energy occurring as a result of the expansion of the low-and higher-pressure steam is converted to alternating current in thepresent case by the electric generator GD coupled to the steam turbineTD. Of course, the two generators GD and G can be physically combined inone unit or mechanically coupled.

The steam produced in the steam generators D₁ and D₂ is advisably usedparticularly for the above-mentioned cooling of the turbine blades andintroduction into the combustion chambers B1 and B2 (also for regulatingthe temperature of the combustion gas). Of course, uses of the generatedsteam outside the process according to the invention are alsoconceivable. However, the proportion of chemically bonded energy of theprimary fuel converted to mechanical or electrical energy is necessarilyreduced in such a case.

In each of the embodiment forms shown in FIGS. 1 to 4 it is assumed thatthe cathode exhaust gas (e.g. PAFC type) contains the H₂ O proportionformed in the fuel cell system FC. However, this need not always be thecase. FIG. 5 shows a variant in a corresponding section of the schematicdiagram of the entire installation in which the fuel cell systemoperates on the basis of an alkaline electrolyte (AFC). In this case, ahydrogen-rich gas is again fed to the anode space via a line 14.However, the water vapor component formed in the fuel cell FC exits thelatter in the anode exhaust gas through line 15. Therefore, in order toobtain steam, a separating unit MD₂ is connected to the line 15. Thesteam which is separated out can be expanded again, for example, in asteam turbine, not shown, through line 23b, while the gaseous part isfed to the combustion chambers (not shown) via line 15c to exploit itscombustible components.

Since the combustion gas from the combustion chambers containscomponents which considerably impair the life of alkaline fuel cells,this combustion gas is advisably not used as cathode gas for the oxygensupply of the fuel cell FC. For this purpose, it is advisable to usefresh air which is compressed in the compressor V to operating pressureand is preheated by indirect means in the air preheater LW by means ofthe heat contained in the combustion gas. The compressor V and the airpreheater LW are connected into the air feed line 18. A correspondingseparating unit MD₁ (e.g. diaphragm filter) can be arranged between thepipelines 11 and 12 so that the water vapor component contained in thecombustion gas can be exploited. The separated steam is drawn off viapipeline 23a and e.g. expanded in a steam turbine.

The efficiency of the process according to the invention is clearlyshown in the following embodiment example which refers to aninstallation configured as shown in FIG. 4. A repeated description ofdetails is therefore unnecessary. However, it should be noted that theutilized mixture of hydrocarbons and water vapor has been heated in theheat exchanger W to preheating temperature for the steam reformers R1and R2. This advisable embodiment form of the invention is not shown indetail in FIG. 4. Precooled air has already been fed to the compressor Kthrough line 1. The steam generated in the steam generator D₁ has beenused in part for cooling the blades of the compressor drive turbine KTand supplied in part to the combustion chamber B1. In a correspondingmanner, the steam generated in the steam generator D₂ is used in partfor cooling the blades of the gas turbine T or guided into the secondcombustion chamber B2. Another portion of the generated steam served ascharging material for the two steam reformers R1 and R2. The processflow can be gathered from the following tables listing the essentialprocess parameters:

    ______________________________________                                        Utilized fuel:        natural gas                                                                   (predominantly CH.sub.4)                                compressor K:                                                                 inlet temperature     4° C.                                            outlet temperature    160° C.                                          outlet pressure       4 bar                                                   heat exchanger W:                                                             temperature increase of combustion air                                                              405 K.                                                  temperature drop of combustion gas                                                                  305 K.                                                  combustion chamber B1:                                                        temperature increase due to combustion                                                              685 K.                                                  compressor drive turbine KT:                                                  inlet temperature     1250° C.                                         pressure ratio of turbine                                                                           1.45                                                    outlet temperature    1150° C.                                         Reformer R1:                                                                  inlet temperature of superheated                                                                    550° C.                                          hydrocarbon/steam mixture                                                     outlet temperature of the combustion gas                                                            610° C.                                          outlet temperature of hydrogen-rich gas                                                             720° C.                                          combustion chamber B2:                                                        temperature increase due to combustion                                                              595 K.                                                  gas turbine T:                                                                inlet temperature     1205° C.                                         pressure ratio        2.47                                                    outlet temperature    980° C.                                          steam reformer R2:                                                            inlet temperature of the hydrocarbon/                                                               550° C.                                          steam mixture                                                                 outlet temperature of combustion gas                                                                610° C.                                          outlet temperature of hydrogen-rich gas                                                             720° C.                                          steam generator D.sub.1 :                                                     water inlet temperature                                                                             15° C.                                           steam outlet temperature                                                                            290° C.                                          steam pressure        4.5 bar                                                 temperature drop of the combustion gas                                                              130 K.                                                  fuel cell:            PAFC type                                               cathode gas inlet temperature                                                                       175° C.                                          cathode gas outlet temperature                                                                      200° C.                                          anode gas inlet temperature                                                                         175° C.                                          anode gas outlet temperature                                                                        200° C.                                          cooling of the fuel cell by                                                   generation of high-pressure steam                                             air heater LW.sub.2 :                                                         inlet temperature of the air                                                                        15° C.                                           temperature increase of the air                                                                     160 K.                                                  temperature drop of the combustion                                            gas partial flow      150 K.                                                  steam generator D.sub.2 :                                                     water inlet temperature                                                                             15° C.                                           steam outlet temperature                                                                            185° C.                                          steam pressure        3 bar                                                   temperature drop of the combustion gas                                        partial flow          100 K.                                                  steam turbine TD:                                                             high-pressure steam inlet temperature                                                               165° C.                                          high-pressure steam inlet pressure                                                                  6.5 bar                                                 low-pressure steam inlet temperature                                                                100° C.                                          low-pressure steam inlet pressure                                                                   1 bar                                                   condenser pressure    0.15 bar                                                electric lines:                                                               generator G of the gas turbine T                                                                    1860 KW.sub.el                                          generator GD of the steam turbine TD                                                                1935 KW.sub.el                                          fuel cell FC          16375 KW.sub.el                                         electrical efficiency based on                                                                      75.2%                                                   net calorific value                                                           ______________________________________                                          In comparison to the known processes for generating electrical or     mechanical energy from fossil fuels, the process according to the     invention not only has a considerably higher efficiency and accordingly     releases considerably less CO.sub.2 in relation to the electrical output,     but also supplies an exhaust gas with a minimum content of nitric oxides.     In addition, valuable process water which can be used for other purposes     occurs as a by-product.

It is particularly advantageous that the "combustionchamber/turbine/reformer" unit combination which is duplicated (seriallyconnected) in FIGS. 3 and 4 can be identically constructed in practiceand integrated in a housing so that a comparatively simple andinexpensive construction of an installation according to the inventionis ultimately made possible in spite of a relatively complicated overallconnection.

What is claimed is:
 1. Process for the combined generation of electricaland mechanical energy from the oxidation of fuel, said processcomprising the steps of:generating a hydrogen-containing gas byendothermic reaction of hydrocarbon compounds in at least one stage withindirect heating of the endothermic reaction; guiding at least a portionof the hydrogen-containing gas generated in the endothermic reaction asanode gas through a fuel cell system for generating electrical energy;introducing the anode gas exhausted from the fuel cell system containinga residual content of hydrogen in at least one combustion stage forgenerating a hot combustion gas at increased pressure; compressing anoxygen-containing gas; introducing the compressed oxygen-containing gasinto the at least one combustion stage for generating the hot combustiongas; generating mechanical energy by means of at least partial expansionof the hot combustion gas in at least one gas turbine; indirectlyheating the endothermic reaction using at least a partial flow of the atleast partial expansion of the hot combustion gas, wherein thecombustion gas is partially cooled in the endothermic reaction:supplying the mechanical energy generated in said generating step forthe compression of the oxygen-containing gas; heating the compressedoxygen-containing gas by indirect heat exchange with the partiallycooled combustion gas in the endothermic reaction; generating thecombustion gas having increased pressure with surplus oxygen; andfeeding the partially expanded combustion gas from the at least one gasturbine to the fuel cell system as cathode gas after conveying heat tocompressed oxygen-containing gas.
 2. A process according to claim 1,wherein the fuel cell system comprises a low-temperature fuel cellselected from the group consisting of electrolytes based on phosphoricacid (PAFC), alkali (AFC) and solid polymers (SP(E)FC).
 3. A processaccording to claim 2, wherein the generation of the combustion gashaving an increased pressure is effected in at least two stages.
 4. Aprocess according to claim 3, wherein the combustion gas is at leastpartially expanded in a gas turbine after every combustion stage.
 5. Aprocess according to claim 4, wherein the combustion gas, which is atleast partially expanded, is used subsequent to the gas turbine for theindirect heating of a stage of the endothermic reaction.
 6. A processaccording to claim 5, further comprising the steps of:collecting partialquantities of hydrogen-containing gas generated in the at least onestage of the endothermic reaction; and supplying the collected partialquantities of hydrogen-containing gas to the anode space of the fuelcell system.
 7. A process according to claim 1, further comprising thestep of subjecting the generated hydrogen-containing gas to apurification so that gas components are separated out prior to being fedto the fuel cell system, and wherein the separated gas componentscontaining combustible components are used in generating the combustiongas.
 8. A process according to claim 1, wherein natural gas is used inthe generation of the combustion gas.
 9. A process according to claim 1,further comprising the steps of:extracting residual heat of the cathodeexhaust gas of the fuel cell system; and supplying the residual heat toprocesses independent of the generation of one of mechanical andelectrical energy.
 10. A process according to claim 1, furthercomprising the step of separating water formed in the fuel cell systemand the generation of the combustion gas at least in part from the fuelcell exhaust gas.
 11. A process according to claim 10, wherein the wateris separated out in the form of water vapor.
 12. A process to claim 11,wherein the fuel cell system is cooled and accompanied by the generationof water vapor.
 13. A process according to claim 12, further comprisingthe step of providing the water vapor to a steam turbine process forwork output.
 14. A process according to claim 13, further comprising thestep of condensing the water vapor after expansion in the steam turbineprocess to below-atmospheric pressure for obtaining process water.
 15. Aprocess according to 14, further comprising the step of generating watervapor by indirect heat exchange using a portion of the heat contained inthe combustion gas.
 16. A process according to claim 15, furthercomprising the step of cooling the turbine blades with at least aportion of the water vapor.
 17. A process according to claim 16, furthercomprising the step of guiding at least one portion of the water vaporinto a combustion space in which the combustion gas is generated.
 18. Aprocess according to claim 17, further comprising the step of providinga portion of the water vapor as charging material for the endothermicreaction of the hydrocarbons running as steam reformation.
 19. A processaccording to claim 1, further comprising a step of converting thegenerated mechanical energy into electrical alternating current by meansof a generator system.
 20. An apparatus for the combined generation ofelectrical and mechanical energy from the oxidation of fuel comprisingacompressor system for compressing oxygen-containing gas; at least onecombustion chamber for at least partial combustion of ahydrogen-containing gas; gas turbine means comprising at least one gasturbine for supplying mechanical energy to an external apparatus and forsupplying drive energy for said compressor system; first pipeline meansfor feeding the compressed oxygen-containing compressed gas to said gasturbine means after passing through said at least one of said combustionchambers in the form of hot combustion gas; at least one reactor for anendothermic reaction for generating a hydrogen-rich gas which is heatedindirectly by the hot exhaust gas of said gas turbine means; a fuel cellsystem comprising an anode space and a cathode space; second pipelinemeans for feeding the hydrogen-rich gas to said anode space of said fuelcell system; third pipeline means for feeding the gas containing aresidual amount of hydrogen to said at least one combustion chamber fromthe output of said anode space; a heat exchanger for heating thecompressed oxygen-containing gas; fourth pipeline means for feeding theturbine exhaust gas to said heat exchanger for heating the compressedoxygen-containing gas after yielding heat in said at least one reactor;and fifth pipeline means for feeding the turbine exhaust gas to saidcathode space of said fuel system as oxygen-containing gas.
 21. Anapparatus according to claim 21, said fifth pipeline means guides theturbine exhaust gas from said at least one reactor to said cathode spaceof said fuel cell system.
 22. An apparatus according to claim 20,further comprising a sixth pipeline means for guiding the turbineexhaust gas from said heat exchanger to said cathode space of said fuelcell system.
 23. An apparatus according to claim 20, wherein said gasturbine means comprises a first gas turbine for driving said compressorsystem and at least one second gas turbine independent from said firstgas turbine for generating the output mechanical energy.
 24. Anapparatus according to claim 20, wherein said at least one combustionchamber is arranged between said compressor system and gas turbinemeans.
 25. An apparatus according to claim 20, wherein said gas turbinemeans is arranged in series with respect to the passage of thecombustion gas.
 26. An apparatus according to claim 20, furthercomprising at least one gas purification installation arranged in saidsecond pipeline feeding of the hydrogen-rich gas to said anode space ofsaid fuel cell system.
 27. An apparatus according to claim 20, furthercomprising an electric generator coupled to said gas turbine means forgenerating electrical energy.
 28. An apparatus according to claim 27,further comprising an invertor coupled to said fuel cell system forgenerating alternating electrical current.
 29. An apparatus according toclaim 27, wherein said fuel cell system is electrically coupled withsaid electric generator.
 30. An apparatus according to claim 20, furthercomprising a separating device and eighth pipeline means for guiding thewater formed from exhaust gas from one of said cathode and exhaust ofsaid fuel cell system to said separating device, wherein said separatingdevice separates the water formed from the exhaust gas as steam.
 31. Anapparatus according to claim 20 further comprising a fresh air feed andat least one preheater, wherein said cathode space of said fuel cellsystem is connected with said fresh air feed, and wherein said fresh airfeed is connected to said at least one air preheater and heatable withthe combustion gas.
 32. An apparatus according to claim 20, wherein saidat least one reactor for the endothermic reaction comprises at least onesteam reformer.
 33. An apparatus according to claim 20, furthercomprising at least one heat exchanger for transmitting heat indirectlyfrom the hydrogen-rich gas generated in said at least one reactor to thehydrogen-containing gas to be fed to said at least one combustionchamber.
 34. An apparatus according to claim 20, wherein said fuel cellsystem comprises a low-temperature fuel system having electrolytesselected from the group consisting of on phosphoric acid (PAFC), alkali(AFC), and solid polymers (SP(E)FC).